This invention relates to an elevator call button assembly and more specifically to a replacement unit for an elevator touch button assembly.
In automatic elevator systems, each floor is provided with call buttons for summoning the elevator to the floor. In addition, there is generally provided a panel in the elevator which includes a series of call buttons utilized to provide a signal to control circuitry that the elevator should stop at a particular floor. The call buttons are generally identified by a floor designation which typically illuminates when selected by a passenger. Upon entry into the elevator, the passenger presses the desired call button identifying a particular floor on which he wants the elevator to stop. Typically, as soon as the call button is depressed, a light will go on, displaying the selected floor. The light can either be part of the call button itself, or can be provided on a separate panel.
In addition to the call button panel provided in the elevator, there is usually a master control panel provided for the main operator or starter. On the starter panels there are also provided call buttons which can control the stopping of the elevator at a particular floor. These also provide illumination either as part of the call button or in an auxiliary panel, indicating the floor on which the elevator will stop.
Many of the call buttons utilized are part of mechanical switches which remain closed once activated. The closing of the switch interconnects specific circuitry to provide the necessary signal to the control system so that the elevator will stop at the particular selected floor. Additionally, the closure of the switch also completes a circuit activating an illumination means to provide a display to the passengers on the elevator that the elevator will stop at the selected floor.
Other types of call button switch circuits utilize relay coils which are energized with current to provide holding power to the coil. However, the holding power is insufficient to bring the switch into a closed position. However, when the switch is manually closed by means of the call button, it is brought into close contact with the coil and the minimal current will be sufficient to maintain the switch in its closed position. To release the button, the coil circuit is opened disconnecting the coil and completely de-energizing it. Such type of energized coil control button is described in U.S. Pat. No. 2,738,489.
A more recent development for a call button is the electronic touch button unit. One such unit is provided by the Otis Elevator Company. The electronic touch button includes a proximity detector wherein the body of the passenger acts as an antenna. The touch button contains a gas tube in an enclosed glass envelope with the bulb exposed. The gas tube normally provides a voltage drop equal to the voltage of the nominal power supply, typically 135 volts. When the passenger comes into contact with the touch button, the voltage across the tube suddenly drops from the nominal power supply voltage to a reduced voltage, typically 72 volts. The sudden drop in voltage produces a pulse which actuates a remotely located electronic circuit to provide the information needed to have the elevator stop at the designated floor. Simultaneously, the touching of the button and the voltage drop ignites the gas tube to provide illumination of the touch button itself which gives the necessary display of the designated floor.
Because the conventional electronic touch button utilizes an exposed gas tube, it is very susceptible to breakage and vandalism. Frequently, the bulb is broken either purposely or inadvertently. For example, heaving or pushing against the button may damage and break the bulb. Many times, passengers with sharp objects, such as the tip of an umbrella, may poke against the touch button and completely shatter the bulb. Replacement of the electronic touch button is costly.
As a result, in many buildings, it is desired to replace the electronic touch button with a manual, tamper proof button system which is cheaper and not as susceptible to breakage and vandalism. However, existing call buttons are not of the type which can produce the equivalent voltage drop from the nominal power supply voltage to the desired reduced voltage, while maintaining a desired current through the button. Furthermore, existing call button circuits are not of the type which provide instantaneous closure of the switch and subsequent release thereof. As a result, in order to replace the electronic touch button, it would be necessary to completely remove all of the circuitry and replace the entire control system. Additionally, it would require mechanical changes to the elevator car entrance panels, the junction box, and would substantially modify the entire control system.